Fourier transform infrared spectroscopic analysis of the degradation of structural lumber in Horyu-ji temple

Horyu-ji temple was built at the end of the seventh century in Nara prefecture, Japan. It remains the oldest existing wooden building in the world. Degradation of its structural lumber was monitered by fourier transform infrared (FT-IR) spectroscopy using some accessories such as a diffusereflectance unit, a microscope system, and fiber optics with a diffuse reflectance probe. Fundamental conditions for the FT-IR measurements were researched with modern hinoki (Chamaecyparis obtusa Endl.), previously. The results obtained were as follows: Purging of instruments with nitrogen gas was essential. The relative humidity of the air, which the sample was placed on, had no influence on the spectra. Extraneous components of the sample had no influence on the spectra. The sizes of meal samples had no influences on the spectra of the diffuse reflectance FT-IR (DRIFT) measurements. Appropriate sections for the microscopic FT-IR (IMR) measurements were radial and tangental sections. By the use of fiber optics with a diffuse reflectance probe, DRIFT spectra could be measured from whole sample surfaces. Based on these results, spectra were measured from the structural lumber. The DRIFT spectra indicateded that the Iignin moiety degraded remarkably on the surface portion because of the weak absorption strength at 1510 cm(-1). The IMR spectra suggested that there is a difference in degradation between earlywood and latewood portions. An absorption strength map of 1510 cm(-1) made up by mapping measurments of IMR indicated clearly that degradation became strong close to the surface. From any point on the structural lumber surfaces, DRIFT was measured by the use of fiber optics with a diffuse reflectance probe. Features of these spectra were compatible with that of the degraded portions of the structural lumber. Thus, this technique was effective in recognizing the degradation of a cultural property without destructive sampling.